Apparatus for drilling a small borehole downwardly from the bottom of a large borehole

ABSTRACT

A small borehole drilling tool, lowered into a large borehole tubular drilling bit, includes a drill shaft interconnected to the large borehole drilling bit through driving drums for common rotation therewith. The small borehole drilling tool further includes upwardly of the drill shaft a coaxial neck, and an annular seal interposed between the neck and the inner wall of the large borehole drilling bit to form a drilling fluid chamber which receives and retains drilling fluid which in turn produces a downward thrust force on the upper surface of the annular seal to force the small borehole drill shaft downwardly into the earth during rotation thereof.

United States Patent Cobbs [451 Jan. 18,1972

[54] APPARATUS FOR DRILLING A SMALL BOREHOLE DOWNWARDLY FROM THE BOTTOMOF A LARGE BOREHOLE James H. Cobbs, Tulsa, Okla.

[ 73] Assignee: Fenix 8: Scisson, Inc., Tulsa, Okla.

[22] Filed: Dec. 2, 1969 [21] Appl. No.: 881,394

[72] Inventor:

840,744 l/l907 Boof ..175/258 Primary Examiner-James A. LeppinkAttorneyl-lead & Johnson 571 ABSTRACT A small borehole drilling tool,lowered into a large borehole tubular drilling bit, includes a drillshaft interconnected to the large borehole drilling bit through drivingdrums for common rotation therewith. The small borehole drilling toolfurther includes upwardly of the drill shaft a coaxial neck, and anannular seal interposed between the neck and the inner wall of the largeborehole drilling bit to form a drilling fluid chamber which receivesand retains drilling fluid which in turn produces a downward thrustforce on the upper surface of the annular seal to force the smallborehole drill shaft downwardly into the earth during rotation thereof.

PATENTEUJAN18 $972 IV/,IIIIIMV/AII /9 71L p i1 I 4 fl] I I TNT 7 3 i /HI I lm BIL i I/VVE/VTOR JAMES H. COBBS WfM ATTORNEYS DOWNWARDLY FROM THEBOTTOM OF A LARGE BOREI'IOLE BACKGROUND OF THE INVENTION Often it isdesirable to drill a small borehole into the earth downwardly from thebottom of a large borehole. For example, the need for a small boreholeextension downwardly of a large borehole is illustrated in my pendingU.S. application, Ser. No. 837,477 entitled Method and apparatus ForMeasuring In situ The Earth Stress At A Preselected Subterranean Area.

Presently, the drilling of such a small borehole is accomplished byfirst drilling the large borehole to a depth immediately above thatdesired for the small borehole. Then the largeborehole drill is raisedout of the hole, and the small borehole drill is lowered to the bottomof the borehole for the drilling of the small borehole. Removing thedrill string by which the large borehole drill is suspended and rotatedrequired a substantial amount of time and energy.

In addition, in small borehole drilling methods presently being used,the small borehole drill string must be of a length at least equal tothe depth of the large borehole, which often is 200 feet or more.Because of the required long length and relative small diameter thereof,a small borehole drill shaft rotating within the large diameterborehole, has a tendency to bow during the drilling operation.

It is therefore an object of this invention to provide an apparatus fordrilling a small diameter borehole extension to a large diameterborehole.

More particularly, an object of this invention is to provide anapparatus wherein a small borehole can be drilled downwardly from thebottom of a large borehole without requiring removal of the largeborehole drill string.

SUMMARY OF THE INVENTION Generally, the apparatus comprises a hollowsplined drill shaft which terminates on the lower end thereof with abit. Coaxially connected to the upper end of the drill shaft is a drivedrum having on the outer periphery thereof driving lugs which engageflutes on the inner wall of a tubular large borehole drilling or coringtool affixed to the lower end of a rotatable drill string in a largeborehole. Rotation of the large borehole drilling tool causes rotationof the small borehole drilling tool. Extending upwardly from the drivedrum is a hollow neck having an annular sealing means which forms incooperation with the neck and the inner wall of the large borehole drillstring a fluid chamber such that fluid pumped into the interior of thelarge borehole drilling tool creates a downwardly acting hydraulicthrust force to cause the rotating small borehole drilling tool topenetrate the earth.

To facilitate rotation of the small borehole drilling tool a second oralignment drum can be utilized for interconnecting the small boreholedrilling tool with the large borehole drilling tool at a lower point.

DESCRIPTION OF THE DRAWINGS is an element of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the lowerportion of a large diameter borehole which extends to the earthssurface. A small diameter borehole 12 is to be drilled from the bottomof large borehole 1,0. The words large' and small" as describingboreholes 10 and 12 are not intended to mean specific dimensions but areemployed to distinguish boreholes l0 and 12 from each other. Typically,borehole 10 will be of a size to accommodate standard drilling tools andequipment such as presently utilized in the oil industry.

Positioned in large borehole 10 is a tubular large borehole drilling orcoring tool 14 which terminates, on the lower end thereof, with atubular coring bit 16. Coring bit 16 may typically include the use ofdiamonds or other abrasive drilling devices well known in the art.Square walled flutes 18 in the inner wall of tubular drilling tool 14extend from the coring bit 16 part way up the inner wall of tool 14, andhave a longitudinal length substantially equal to the desired depth ofsmall borehole 12. Flutes 18 are paralleled to each other and equallyspaced, as shown in FIG. 2. Large drilling tool 14 is affixed to thelower end of a drill string 19 which extends to the earth's surface.Drill string 19 provides means of rotation of the large drilling toolandalso forms a conduit or supplying drilling fluids to the large drill.

Coaxially disposed within the hollow interior of large borehole drillingtool 14 is a small borehole drilling tool tool generally indicated bythe numeral 20 which includes; a small diameter externally splined drillshaft 22; an upper driving drum 24; a lower alignment drum 26; and anupstanding neck portion 28.

The small borehole drill shaft 22 is tubular in shape and terminates, onthe lower end thereof with a coring bit 30. Bit 30 may also be of thenoncoring type. Longitudinal splines 32 on the outer periphery of shaft22 are at equally spaced interval as shown in FIG. 2.

An inner core barrel 34 is coaxially disposed in the hollow interior ofdrill shaft 22. Inner core barrel 34 has a length substantially equal tothat of shaft 22 and has an outer diameter less than the inner diameterof shaft 22 so as to provide an an-' nular fluid passageway 36therebetween.

Looking now at the upper end of shaft 22, rigidly and coaxially securedthereto is a cylindrical upper drive drum 24 having neck portion 28affixed to and extending upwardly therefrom.

Below upper drive drum 24 is lower alignment drum 26 which rests on thebottom of large borehole 10. The lower alignment drum 26 has an axialopening 38 therethrough having equally spaced grooves 39 therein (seeFIG. 2) to match and slidably receive splines 32 such that the drum isrotationally locked to shaft 22. The lower alignment drum 26 ispermitted to travel longitudinally relative to shaft 22 and rides on thebottom of large diameter hole 10.

Attached to each of drums 24 and 26 on the outer periphery thereof are aplurality of equally spaced driving lugs 40 which project outwardlytherefrom to engage flutes 18 in the inner wall of large boreholedrilling tool 14, thereby rotationally interconnecting shaft 22 anddrilling tool 14. As shown in FIG. 3, driving lugs 40 are comprised offlat plate portions 42A, 42B, 42C, 42D, 42 E, sequentially pivoted toeach other to form a unitary linkage. Plate portions 42A and 42E haveattached to the upper and lower edges respectively one end of expansionsprings 44A and 448. The opposite ends of springs 44A and 44B aresuitably secured to notches 46 in drums 22 and 24 so as tolongitudinally and inwardly bias plate portions 42A and 42B which inturn through the pivotal linkage of portions 44B and 44D outwardly biasportion 42C to assure tight engagement thereof in flutes l8.

Coaxially affixed to the upper end of driving drum 24 over the centralaperture 24A thereof is the annular hollow upstanding neck 28.Communication with fluid passageway 36 in shaft 22 is provided throughthe central opening 24A in drum 24 with the interior of neck 28 andthrough apertures 28A with the interior of large diameter drilling tool14.

Received on the upper end of the upstanding neck 46 is a conical-shapedattachment cap having a base of a greater diameter than that of the neckto provide means for receiving and retaining a wireline tool, such ascommonly used in the art, utilized in lowering or raising the smallborehole drilling tool 20 into or from the interior of the largeborehole drilling tool 14.

An annular resilient seal 48 is interposed between the inner wall of thelarge borehole drilling tool 14 and the outer wall of neck 28. Seal 48fits firmly against the walls of neck 46 and drilling tool 14 to form incooperation therewith a drilling fluid chamber 50 for receiving drillingfluid pumped thereinto from the earths surface. Chamber 50 serves twopurposes; first, it causes the drilling fluid to impose a hydraulicdownward thrust force on the small borehole drilling tool 20 to forcesmall drill bit 30 into drilling engagement with the earth, and secondit causes drilling fluid to flow through ports 28A for eventual entranceinto fluid passageway 36 to thereby carry away the cutting from smalldrill 30.

In operation, the large borehole is drilled in the standard manner andterminates directly above the desired location of the small borehole.Tubular drilling tool 14 is positioned in borehole 10 as illustrated inFIG. 1. Next small borehole drilling tool is coaxially introduced intothe interior of drill string 19 and lowered into drilling tool 14 bymeans of a wireline tool which grasps cap 47. As the small boreholedrilling tool 20 enters the large diameter tubular drilling tool 14driving lugs 40 on drums 24 and 26 engage flutes 18 to rotationallyinterconnect small borehole drilling tool 20 to tubular drilling tool14. Annular seal 48 forms drilling fluid reservoir chamber 50. Thewireline tool is removed by means well known in the petroleum industry.

With small borehole drilling tool 20 properly positioned at the bottomof borehole 10, drilling fluid is pumped from the earth s surface intochamber 50 and bears against annular seal 48. As the fluid builds up inthe chamber, a portion thereof continuously flows through ports 28A tothe interior of neck 28 and down into passageway 36, within shaft 22.The fluid flows out of shaft 22 and past the lower end of drill 30,carrying cuttings with it and then upwardly in the annular area exteriorof large diameter drill tool 14, carrying cutting from drill 30 to theearth's surface.

Simultaneously with the pumping of the drilling fluid, tubular drilltool 14 is rotated by means of drill string 19 extending to the earth'ssurface in the same manner as rotary drilling is normally accomplished.The rotation of large diameter drilling tool 14 is transferred by lugs40 to upper and lower drums 24 and 26 and by the drums to shaft 22. Therotation of shaft 22 coupled with the downward thrust force exertedthereon by the drilling fluid on annular seal 48 causes core bit 30 topenetrate the earth while drilling fluid flowing through passageway 36carries away the core cuttings. This rotary drilling action causes asmall diameter core 52 to be cut as shaft 22 with drill 30 downwardlyadvances. The core barrel 34 receives the core 52 to help keep it intactand to facilitate subsequent removal of the core in the same manner ascore barrels are typically used in coring operations. Downward movementof drill shaft 22 may be continued until upper drive drum 24 contactslower alignment drum 26.

During the operation utilizing small diameter drilling tool 20 toprovide small borehole 12 the large diameter drilling tool 19 is rotatedbut no weight or downward thrust is applied to the tool 14 so that largediameter hole 10 is not extended. This is accomplished utilizingstandard rotary drilling techniques used in the petroleum industry bywhich the weight of the drilling string 19 and tool 14 is cancelled byupward lifting forces applied at the earth's surface while the drillstring 19 is rotated.

Lower drive drum 26 serves to assist the upper drive drum 24 intransmitting torque from large drilling tool 14 to shaft 22 and at thesame time helps stabilize and align the lower end of shaft 22,especially when the drilling of small diameter hole 12 is first begun.

After the small diameter borehole is drilled to the desired depth awire-line tool may be lowered within the drill string to grasp the cap47 and remove the small diameter drilling tool 20 from the interior ofthe drill string 19 and drilling tool 14. The interior of the drillingstring 19 and tool 14 is then clear for further operations as desired.Following such further operation large borehole 10 may be extended bythe rotation of the drill string 19 and lar e drill tool 14 in theconventional manner. It can be seen that y the apparatus of thisinvention a small diameter borehole 12 followed by a coaxial largediameter borehole 10 may be achieved without the time consumingnecessity of removing the drill string 19 and large diameter tool 14from the hole.

During the detailed description of the preferred embodiments, specificlanguage has been used for the sake of clarity. However, it is to beunderstood that such words are not meant as words of limitation andinclude all equivalent which operate in a similar manner to accomplish asimilar purpose.

What is claimed:

1. An apparatus for drilling a small borehole downwardly from the bottomof a large borehole comprising:

a tubular large borehole drilling tool having internal longitudinalflutes in the lower portion thereof;

means for rotating said large borehole drilling tool from the earthssurface;

a tubular drill shaft coaxially received within the large boreholedrilling tool and having a bit secured to the lower end thereof;

a drive drum rigidly secured to the upper end of said drill shaft andhaving a longitudinal opening therethrough communicating with theopening in said drill shaft whereby drilling fluid introduced in theupper end of said large drilling tool flows downwardly through saiddrive drum, said drill shaft, and out through said bit;

at least one drive lug secured to the outer periphery of said drive drumand extending outwardly therefrom to engage said flutes to causerotation of the drive drum and drill shaft as said large drilling toolis rotated and permitting longitudinal movement of said drill shaft anddrive drum relative to said large borehole drilling tool; and

seal cup means affixed to the upper end of said tubular drill shaft, theseal cup means sealably and slidably engaging the interior of saidtubular large borehole drilling tool providing a fluid chamberresponding to fluid pressure to force said drill shaft downwardly.

2. An apparatus according to claim 1 including:

an alignment drum slidably and nonrotatably received on said drill shaftbelow said first drive drum, said alignment drum having at least onedrive lug secured to the outer periphery thereof to slidably engage theflutes on the interior surface of the large borehole drilling tool.

3. An apparatus as in claim 1 wherein said drive lug on said first drumcomprises:

a plurality of plate portions pivotally secured together to form aunitary outwardly expandable linkage; and

spring means biasing said linkage outwardly from said drive drum.

4. An apparatus according to claim 1 including:

wire-line attachment means secured to said drive drum.

5. An apparatus according to claim 1 including:

an upstanding tubular neck portion projecting from the upper end of saiddrive drum, the tubular interior being in communication with drive drumopening, said neck portion having a fluid passageway aperture therein.

6. An apparatus as in claim 5 including:

wire-line tool attachment means at the upper end of said neck portion.

7. An apparatus as in claim 5 wherein said seal cup means is interposedbetween the outer periphery of said neck portion and the inner peripheryof large borehole drill tool providing a fluid chamber receivingdrilling fluid thereabove.

1. An apparatus for drilling a small borehole downwardly from the bottomof a large borehole comprising: a tubular large borehole drilling toolhaving internal longitudinal flutes in the lower portion thereof; meansfor rotating said large borehole drilling tool from the earth''ssurface; a tubular drill shaft coaxially received within the largeborehole drilling tool and having a bit secured to the lower endthereof; a drive drum rigidly secured to the upper end of said drillshaft and having a longitudinal opening therethrough communicating withthe opening in said drill shaft whereby drilling fluid introduced in theupper end of said large drilling tool flows downwardly through saiddrive drum, said drill shaft, and out through said bit; at least onedrive lug secured to the outer periphery of said drive drum andextending outwardly therefrom to engage said flutes to cause rotation ofthe drive drum and drill shaft as said large drilling tool is rotatedand permitting longitudinal movement of said drill shaft and drive drumrelative to said large borehole drilling tool; and seal cup meansaffixed to the upper end of said tubular drill shaft, the seal cup meanssealably and slidably engaging the interior of said tubular largeborehole drilling tool providing a fluid chamber responding to fluidpressure to force said drill shaft downwardly.
 2. An apparatus accordingto claim 1 including: an alignment drum slidably and nonrotatablyreceived on said drill shaft below said first drive drum, said alignmentdrum having at least one drive lug secured to the outer peripherythereof to slidably engage the flutes on the interior surface of thelarge borehole drilling tool.
 3. An apparatus as in claim 1 wherein saiddrive lug on said first drum comprises: a plurality of plate portionspivotally secured together to form a unitary outwardly expandablelinkage; and spring means biasing said linkage ouTwardly from said drivedrum.
 4. An apparatus according to claim 1 including: wire-lineattachment means secured to said drive drum.
 5. An apparatus accordingto claim 1 including: an upstanding tubular neck portion projecting fromthe upper end of said drive drum, the tubular interior being incommunication with drive drum opening, said neck portion having a fluidpassageway aperture therein.
 6. An apparatus as in claim 5 including:wire-line tool attachment means at the upper end of said neck portion.7. An apparatus as in claim 5 wherein said seal cup means is interposedbetween the outer periphery of said neck portion and the inner peripheryof large borehole drill tool providing a fluid chamber receivingdrilling fluid thereabove.